As you can see it has more features, A hide Winterboard toggle, debug logging, Summerboard mode (for all those old themes), select themes (the current Winterboard themes, see image below) and optimize themes for a speedier device.

SummerBoard was the previous theme manager before WinterBoard. These are all plays on the fact that the core of the iPhone experience is the SpringBoard. In any case, SummerBoard themes were very simple. They did not have fancy animated wallpapers or even the ability to modify UIImages, such as the images for the navigation bars, etc. Most themes are optimized for SummerBoard. Rather than allocating more resources, you can switch on SummerBoard Mode and only modify the status bar, wallpaper, icons, and dock.